Thermostatic switches



July 3, 1956 c. s. MERTLER 2,753,421

THERMOSTATIC SWITCHES Filed March ll, 1953 4free/Veys United States Patent O THERMOSTATIC SWITCHES Charles S. Mertler, Mansfield, ho, ass'gnorgtostevens 'Manufacturing Company, Inc., Mansfield, hio, a corporation of Ohio Application March 11, 1953, Serial No. 341,753

21 Claims. (Cl. 20D- 138) through center, i. e., rapidly reverses its curvature .upon

attaining a predetermined temperature. This reversalfof 'curvature is utilized to control the movement of ya contact Vor contacts of the switch. However, 'in prior switches of this type the bimetallicdisc is feith'er firmly clamped, adjacent the periphery or'the centralportion thereof, or the disc is provided with openings and/or'has contacts or the like vconnected thereto. `Such f clamping of the disc, provision of openings therein, and connection `of parts thereto alters the response of the discwith -the result that the switch operation tends to be :erratic and requires a `comparatively large temperature differential.

An object of the invention'is yto provide-animproved snap acting thermostatic switch ofthe bimetallic disc-type which is reliable and rapid in action and which maybe readily calibratedafter assembly.

Another object ofthe invention is -to provide an imkproved snap acting thermostatic switch employing a'bimetallic disc in which the disc has no operating-parts connected thereto and is supported ina manner-such that iiexing thereof is unrestrainedwhereby the'switch .operation effected by the said iiexing occurs substantially uniformly at-a predetermined temperature.

An Vadditional object of theV invention .is'to'providean improved snap acting switch `as defined -above wherein creepage orV other lost motion of the bimetallic-.foperating disc may befelirninated, thereby preventing frying .of the contacts, without affecting the uniformityof response of the Switch upon attainmenty of lapredetermined temperature. n

-A further object of the invention is to provide van improved snap acting switch employing sa yAbimetallicfdisc as the operating member, which disc is vfreely-supported adjacent its periphery and is engaged by amotion ltrans-A mitting member adjacent the center for veffecting the switchoperation, the member supporting thedisc-having a threaded connection with va base member carryingthe .stationary contact means of the switch so that the switch operationmay be regulated by relative rotation of ithe members.

Arstill further object of the invention is to provide an improved snap acting switch as defined above wherein the movable contact is ycarried by `a4 resilientV armV sotmounted that .there isa wiping action between the movable 4and stationary contacts when said switch is operated.

A more specific object of the invention Vis to -providean improved snap acting thermostatic switch as .heretofore defined wherein the said disc supporting memberhas-a planar. surface upon whichthe said bimetallic disc is-supported .adjacent its periphery with the .central .portion of the disc unsupported and free to flex.

A still more specific object of theA invention is tofpro- .22 freely'extends. head 22a located between the sheets of :insulating mateice Ku vide an improved thermostatic switch as defined above and wherein the bimetallic disc supporting member is substantailly cup-shaped with the disc supporting surface interiorly thereof and spaced below the rim of the member, the said member and the base member on which the 4stationary switch contact means are mounted being provided with the aforementioned cooperating screw threads which permit the switch operation to be adjusted )by relative rotation of the members.

The invention further resides in certain novel features of the construction and in the combination of the parts of .apparatus in which the invention is embodied, and further objects and advantages of the invention will be apparent to those skilled in the art to which the invention .pertains from the following description of certainembodiments thereof described with reference to the accompanying drawing, forming a part of this application, in which,

lFig. 1 is an enlarged longitudinal sectional view through .the presently preferred form .of a thermostatic switch'embodying the invention, the switch being shown in circuitclosing position;

Fig. 2 is an enlarged longitudinal Sectional view through a modified form of a thermostatic switch constructed in yaccordance with this invention, the 'switch contacts .being illustrated in circuit closing position;

Fig. 3 is an `enlarged longitudinal sectional view through Vanother modified form of a thermostatic switch constructed in accordance with this invention, the switch contacts being shown in circuit closing position, and

Fig. 4 is an enlarged longitudinal sectional view through a further modified form of a thermostatic switch constructed in accordance with this invention, the switch contacts being shown in circuit closing position.

The thermostatic switch illustrated in Fig. 1 of the drawings is of the enclosed type and comprises a base member 10 which is adjustably connected with a substantially cup-shaped member 11. As here shown, ythe base member 10 is formed by a metal disc 12 and is provided with spaced stationary contacts 13 and 14, which are secured to and insulated from the disc or member 12. Thus, the illustrated contacts 13 and 14 are ythe headed portions of rivets or studs, the reduced diameter Shanks 15 of which passes through openings of 4larger diameter in the plate or disc 12 with the contact studs being insulated from the member 12 by sheets of insulating material `16, 17a and 17b, such as mica or the like, placed on opposite ysides-of the member of disc 12. The contacts 13 and 14 are connected, respectively, with angle-shaped terminal .members 18 and 19 by having the shank 15 of a contact stud pass through an opening in one leg of the correspond- 'ing-terminal member, the contact studs being secured to the base member or disc 12, and to the terminal members,

v.bypeening or otherwise upsetting the outer end of the shank of the studs as will be apparent from Fig. fl andas will be readily understood by those skilled in the art. The contact surfaces of the contact members 13 and 14 may beplated or otherwise .provided with a layer V20 of silver or other suitable contactmaterial.

.closing of this circuit is theneifected by means of a con- -ductive member 21 which is-movable toand from bridging engagement with the contacts 13and 14. ln the illustrated embodiment, the conductive fmember Y21 is `shown as formed of metal and has a substantially disc shape with a central opening through which a-guide'stud The guide stud 22 has an enlarged rial V17a and 17b with the shank of the studextending through an opening inthe sheet 17b substantially centrally of the stationary contacts 13 and 14 as will be apparent from Fig. 1. The size of head 22a and the thickness of the sheet 1'7b are such that the stud is iirmly retained in place and the sheets 17a and 17b also serve to insulate the stud from the base.

The conductive member 21 is continuously urged to circuit opening position by a spring means 23 acting between the base and conductive member 21. In the preferred construction, the spring means 23 is a helical compression spring disposed about the stud 22 and positioned between the base and the conductive member 21 so that the force of the spring normally tends to separate the member 21 from engagement with contacts 13 and 14.

The position of the conductive member 21, and hence the operation of the switch, is controlled by a bimetallic disc 24 which is conveXo-concave or dish-shaped and is loosely supported adjacent its periphery with the disc free to reverse its curvature in response to a predetermined temperature change which reversal of curvature is employed to control the movement of the conductive member 21. In the preferred construction, the support for the thermostatic switch disc 24 is an annular shoulder providing a substantially planar surface 25 in the cupshaped member 11 adjacent the bottom thereof with the peripheral region of the bimetallic member freely supported thereon, the height of the surface 25 from the base of the cup-shaped supporting member being such that the central portion of the bimetallic disc 24 does not contact the said supporting member when it fiexes from the position shown in solid lines in Fig. 1 to its other position as indicated in broken lines in that figure. This reversal of curvature of the bimetallic member controls the switch operation by means of a motion transmitting means positioned between the central portion of the bimetallic disc 24 and the conductive member 21. As here illustrated, the motion transmitting means is a thimble-like member 26, formed of insulating material such as ceramic or the like, which is freely slidable on the outer portion of the guide stud 22. The lower curved end of the motion transmitting member 26 engages the bimetallic disc 24 adjacent the central portion thereof and is maintained in contact therewith by the spring means 23.

In the illustrated embodiment, the bimetallic disc 24 is shown as being so curved and mounted that the conductive member 21 is maintained in circuit closing position, that is, in bridging engagement with the stationary contacts 13 and 14, against the force of the spring 23. However, upon the attainment of a predetermined temperature, the bimetallic disc 24 will reverse its direction of curvature with a snap action whereupon the motion transmitting member 26 and the conductive member 21 will. move axially of the stud 22 under the force of the spring 23. This movement of the conductive member 21 from` engagement with the stationary contacts 13 and 14 is rapidly effected and hence may be termed a snap action. When the temperature to which the bimetallic disc 24 is subjected returns to a value which causes the disc to again reverse its direction of curvature, the reversal will again occur with a snap action and the movement of the central portion of the disc will be transmitted by the member 26 to the conductive member 21 so that the latter reengages the stationary contacts 13 and 14. lt will be evident that all portions of the bimetallic disc 24 are free to flex in effecting such reversals of curvature since no part of the disc is clamped or otherwise held rigid. Also, the disc has no openings therein or parts rigidly connected thereto which would alter the flexing of the disc. Hence, the reversals of curvature of the disc, and therefore switch operations, are stable and occur within a comparatively narrow temperature differential.

An important feature of this invention resides in the manner in which the switch mechanism is constructed so that its operation may be readily adjusted after the switch 'has been assembled and without unequally stressing dif,-

ferent parts of the bimetallic disc. This is achieved by providing a screw threaded connection between the base and the bimetallic disc supporting members so that compression of the spring 23, and hence the force exerted on the bimetallic disc 24, which determines the switch operating temperature, may be adjusted by relative rotation-` between the members 10 and 11. Thus, as shown in Fig.. 1, the base 10 has the periphery of the metal disc or plate: 12 provided with a screw thread 27 that mates with an: internal screw thread 28 on the inner wall surface of the'. cup-shaped member 11. Hence, by simply rotating the: cup-shaped member relative to the base, or conversel=y the switch may be adjusted to provide contact operatiorn at a predetermined temperature.

The adjustability provided by the threaded connection' between the base 10 and member 11 also permits elimina tion of contact frying by removing creepage of the bimetallic disc. That is to say, when an unrestrained con-A veXo-concave bimetallic disc is subjected to a temperature: change the first response is a relatively slow increase in. the radius of curvature of the disc and the snap action does not occur until a critical point is reached whereupon` the disc snaps through center. This relatively slow' change of curvature is known as creepage and frequently results in contact frying since the contact pres-A sure is reduced by the creepage to the place where slight; vibrations, jolts or the like will cause momentary separa-- tion of the movable contact from the stationary contact; or contacts. This diiculty may be eliminated with switches of the construction here disclosed by effecting: relative rotation between the base and disc supporting; members until the motion transmitting member 26 engages the bimetallic disc 24 with sufficient force so that the latter is deflected an amount substantially corresponding to the aforementioned creepage change in curva-- ture. Consequently, the first movement of a bimetallic: disc thus adjusted is a reversal of curvature, which occurs. with a snap action, and there is no unstable position wherein the contacts can intermittently open and closey due to vibrations or similar disturbances.

When the switch is intended for operation at a single: predetermined temperature, the aforementioned adjust-- ment for operation at a predetermined temperature: and/or to eliminate creepage is made at the factory, in. the nature of a calibration, after which suitable means, such as a drop of sealing wax or solder, may be provided between the base and cup-shaped members to prevent unauthorized relative rotation therebetween. lt will be understood, however, that adjustment of the switch will not be varied simply by repeated operation of the movable contact in response to changes in temperature. Consequently, if an adjustable thermostat is desirable, either the base or the cup-shaped member may be provided with. a means for indicating its rotative position in terms of the resulting operating temperatures of the switch as will be readily understood.

The presently preferred embodiment of the switch illustrated in Fig. 1 of the drawings is of the type in which the movable conductive member is normally held in circuit closing position by the bimetallic disc 24. It will be apparent, however, that the novel features of the switch construction may also be employed with a bimetallic disc which normally permits the conductive member 21 to be spaced from the stationary contacts and is only moved into engagement therewith upon attainment of a predetermined temperature dilerent from that to which the switch is normally subjected. lt will also be apparent that changes may be made in the construction of the switch especially with respect to the materials employed therein. Thus, the base member it) need not be made of metal and provided with separate insulating discs such as 16, 17a and 17b, since this base member may be made of insulating material, such as one of synthetic resins or the like.

`As mentioned heretofore, the switch shown in Fig. l

Fig. `2 of the drawings. .comprises a base member. 30 which may be formed of 'insulating material such as one ofthe synthetic resins. This base member is provided with a piuralityof spaced vStationary contacts 31 and 32, which are adapted' to, be bridiged by a movable conductive member`33. `embodimentvof the invention, the stationaryA contacts13l ,I hermetical sealing. It willbe apparent,'however, .that'the operatingjprinciples of the suitch'wouldnotbechanged if the construction was other than 'that of an'enclosed Switch. 'That is to say, the substantially cup-shaped member 11 need not be provided with an impervious bottom A, portion since the kmaterial centrallyof `the annular shoulder or surface 25 may be omitted incertain instances as,

ynot'only an impervious cup-shaped member but also one which, although substantially cup-shape, hasportions of Ithe bottom or wall omitted.

Another embodiment of the invention .is illustrated in As shown therein, the switch -In this and 32 are each one leg of apair of substantially U- shaped. members, such as 34, the other' leg of each member'34 is secured tothe base'3t'l and to ay terminal member 35, 36 respectively,v by means of a rivet'37. `The con- ,ductive member 33 is preferably "disc-shapedrand has a central opening through which. extends a reduced diameter shank 3S of amotion transmitting member`39 formed of insulating material, such as ceramic or thelike.

The Vlower end ofthe member"39 engages 'the central portionrof a dished bimetallic disc'40. lTheperipheral Aportion of the bimetallic disc 4t) is supported upon'ithe `planar surface of anannular shoulder 41 on amember l42 which is adjustably connected -with the base 30. As here shown, the base 30 isl provided with a cylindrical flange portion 43 which is formed of metal and is secured lto the baseA 30 byhaving spaced portions, suchas44 thereof received in notches or recesses in the periphery of the base 30 and spun or bent over 'the base in a well-known manner. The interior of the cylindrical member 43, adjacent its rim, isr provided with a screw thread 45 which mates with a cooperating 'thread on the memberl42. Consequently, the position ofthe bimetallic disc 40 may be adjusted relative to thevbase3tl by relative rotation between the base 3i) and supporting member 42 in the'same manner 'that adjustment was effected intheembodiment of the switch illustrated in Fig.V l.

`As vdisclosed in Fig. 2, the switch is intended to have the conductive member 33 normally engaged with the stationary contacts ,31 and, 32 under the force of a spring 46, which is preferably of the helical compression type,

acting between the member 33 and the base 30. Thus,

oneend of the spring 46 is received in'a recess in the vbase :30 while the other end of the spring surrounds-the shank 38 of the motion transmitting member "39. In thisposition of the conductive member 33, the bimetallic 'disc 4l) has the convex side disposed outwardly with respect to the contacts, 'the disc being adapted to reverse its 'direction of curvature so as to occupy the position indicated m broken lines in Fig. 2 upon attainment of a predetermined ythe predetermined value at which the bimetallic disc 40 snaps back to the position illustrated in solid lines in Fig. 2. Adustment ofthe switch operating temperature and removal of creepage is effected,vas mentioned above,by relative rotationbetween the base '30 and the discsupporting' member 42.

The switch illustrated in Fig. 3 comprises a base mem- `51, that may be'formed 'of 'metal and` attached' to `the `base in any suitablemanner as,'for example, in the manner explained above for connection of the base 30 and flange-43 in the switch embodiment shown in Fig. v2. The interior of the ange 51, adjacent the rim thereof, is'provided with a screw thread 52 which mates with a cooperating screw thread on an annular member 53 that is similar to the'member 42. VThe member 53, like the member 42, serves as an adjustable support for a dished bimetallicdisc 54, the peripheral portion of which'fre'ely rests upon the planar surface 55 of an annular flange provided onV the .member 53.

.The base 50 is provided with a stationary Contact means 55 with whicha movable contact S6 cooperates,` the position of the latter being governed by the position of the bimetallic disc 54. As here shown, the stationary con- 'tact 55 is the enlarged head of a stud or rivet S7 the shank of whichextends throughv an opening inthe base 59 and a suitable opening in a terminal member 58,the

Vrivet or stud 60 is preferably provided with suitable spacing means, such as an integral shoulder or the' like 62, between the resilient arm59 and the adjacent'portion of the base 50 so that the arm 59 is spaced from the base.

The portion of the resilient arm 59 intermediate its ends is providedwith an opening through which extends theV reduced diameter or shank portion of a motion transmitting member or pin 63, the lower end of which member is curved and continuously maintained in engagement with the central portion of the bimetallic disc by the resiliency of the arm 59. The reduced diameter portion or shank of the member 63 extends beyond the member 59 and is adapted to abuttingly engage a stationary surface to limit movement of the motion transmitting member 63 under inliuence of the action of the bimetallic disc 54 since, in this embodiment of the switch, the distance between the resilient arm 59 and the central portion of the bimetallic disc 54, when the latter has taken the position shown in full lines in Fig. 3, exceeds the value necessary to eifect engagement of the movable contact 56 with the stationary contact 55. Moreover, the strength of the arm 59 is such that it is insuicient to resist movement of the bimetallic disc 54 to its fully operated position shown in Fig. 3. Consequently, when the bimetallic disc 54 is in the illustrated position, the resilient arm 59 is bowed or flexed towards the base '50 intermediate the studk 60 and the stationary contact 55. Preferably, the base 50 is provided with a raised portion or boss 64, intermediate the contact`55 and the arm supporting stud 60, with which the inner end of the reduced diameter portion of the pin 63 engages for the aforementioned limiting of the flexing of the arm 59.

In the form of the switchillustrated in Fig. 3, the normal position of the bimetallic disc is as shown in Vthe drawing and hence the switch is. normally in circuit closing condition. However, upon a predetermined change in temperature, the bimetallic disc 54 will reverse its curvature with a snap action whereupon the resiliency of the arm 59 will cause vthe contact 56 to snap from engagement with contact 55 thereby breaking the circuit through the switch. The motion transmitting member or pin 63 will remain in engagement with the bimetallic member 54 throughout its movement due to the resiliency of the arm 59. Hence, when'the temperature of the bimetallic disc again returnsto normal, the curvature of the bimetallic disc will be reversed with a snap action,

returning to the position shown in Fig. 3, whereupon the resilient arm 59 will be moved to again engage the contact 56 with the contact 55. The circuit through the switch is completed as soon as the contacts have thus reengaged but, as noted heretofore, the central portion of the resilient arm 59 moves beyond the extent necessary to elect reengagement of the contacts, this movement being terminated only when the end of the member or pin 63 engages the abutment 64. This additional movement of the arm 59 etects a slight wiping action between the contacts 55 and 56 thereby maintaining the latter in good electrical conductive condition.

It will be apparent that although the switch described and shown in Fig. 3 is intended to normally maintain the contacts thereof in circuit closing position, the switch construction can be readily altered so that it can be employed with the contacts normally in circuit opening position. Adjustment of the operating characteristics of the switch in Fig. 3 is eiected in the same manner as is the embodiment illustrated in Fig. 2, by relative rotation between the disc supporting member 53 and base Si). Consequently, the switch may be readily calibrated after assembly and the disc supporting member secured in adjusted position relative to the ange 51 by means of solder or the like. Alternatively, the switch may be employed for response to dierent predetermined temperatures by providing either the flange 51 or the supporting member 53 with a convenient manipulating handle and a dial or other suitable indicia to represent the operating condition of the switch for a given relative position of the members 51 and 53.

The embodiment of the invention shown in Fig. 4 is constructed substantially like that shown in Fig. 3 in that it comprises a base 65 and an attached cylindrical member or ange 66, corresponding respectively with the base and flange 5t? and 5l of the previously described embodiment. Likewise, the base 65 in the instant embodiment is provided with a stationary contact 67 at one end of a rivet or stud 63 which also secures the contact and a terminal member 69 to the base 65. The movable contact 70 is carried by a resilient arm 7l, the other end of which is secured to a rivet or stud 72 that also secures a terminal member 73 to the base 65 in the same manner that the resilient arm S9 and terminal 61 are secured in the embodiment shown in Fig. 3. In a similar manner, the switch shown in Fig. 4 is operated by a dished bimetallic disc 74, the peripheral portion of which rests upon a planar surface on an annular shoulder 75 provided in a disc supporting member 76 that has an external screw thread mating with an internal screw thread 77 in the flange 66. The movement of the bimetallic disc 74 is communicated to the resilient arm 71 by a motion transmitting member or pin 78 which has a reduced diameter portion 79 extending through an opening intermediate the ends of the resilient arm 71.

The switch shown in Fig. 4 differs from that shown in Fig. 3 in that the resilient arm 71 is somewhat less flexible and it is not necessary to provide a raised boss or other abutting surface for the end of the portion 79 of the motion transmitting member. However, the arm 71 is suiciently flexible so that it is bowed or curved slightly intermediate its ends when the bimetallic disc 74- has taken the position indicated in the drawing and which causes engagement of the contacts of the switch. Therefore, there is a wiping action between the contacts as in the form of switch shown in Fig. 3. The operation of the switch disclosed in Fig. 4 is substantially the same as explained above in conjunction with Fig. 3 and hence need not be redescribed. Suice it to note that, in this form of the switch as in each of the other embodiments of the invention, adjustment of the operating characteristics of the switch can be readily eiected by relative rotation between the base and the bimetallic disc supporting member.

The embodiments of the invention shown in Figs. 2, 3

8 and 4 have been illustrated as comprising flange portions 43, 51 and 66 which are formed of metal and secured to the base members 30, 5t) and 65, respectively, that are formed of insulating material. It will be evident however that, if desired, these flanges could be formed integrally with the bases, both being formed either of insulating material or of metal. In the event the base should be formed of metal, suitable insulating means would, of course, be provided for the terminals and contacts. It will also be apparent that instead of forming the disc supporting member 42, 53 or 76 in these embodiments as an annular member threaded into a flange of the base, the disc supporting member could be made substantially cup-shaped and have a threaded engagement with the base in the manner illustrated in Fig. 1. Also, as mentioned heretofore, while the several switches have been shown as being of the type which normally maintains the contacts in closed condition, they could be readily constructed, in accordance with the invention, so that the contacts are normally open. These and other changes, which are within the purview of those skilled in the art, are considered as falling within the ambit of the invention and, consequently, the latter is not to be construed as restricted to the specific details here shown and described except as may be required by the spirit and scope of the appended claims.

Having thus described the invention, I claim:

l. A thermostatic switch unit comprising a substantially planar base member, a supporting member interconnected with the base member, and forming therewith a switch housing, said supporting member having a supporting surface located interiorly of said housing in a plane parallel to the adjacent substantially planar side of said'base member, stationary electrical contact means carried by said base member and extending within said housing toward the plane of said supporting surface, electrical contact means in said housing and movable to and from engagement with the stationary contact means and normally biased to one of those positions, a dished bimetallic disc within said housing and adapted to reverse its direction of curvature upon attaining a predetermined temperature and having its periphery freely supported by said supporting surface of said supporting member, and motion transmitting means between the center of said disc and said movable contact means.

2. A thermostatic switch unit comprising a base, stationary contact means mounted on said base, contact means movable to and from engagement with said stationary contact means and normally biased to one of those positions, a dished bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having an imperforate center portion, a member connected with said base and forming a housing therewith, said member loosely supporting said bimetallic disc adjacent the periphery thereof, motion transmitting means between the center portion of said disc and said movable contact means and having a free bearing engagement with said imperforate center portion .of the disc, and means providing a threaded connection between the said member and base whereby relative rotation therebetween adjusts the position of said bimetallic disc relative to said base and thereby adjusts the operation of the switch.

3. A thermostatic switch unit comprising a base, stationary electrical contact means mounted on said base, electrical contact means movable to and from engagement with said stationary contact means and normally biased to one of those positions, a dished bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having an imperforate center portion, a member having a planar surface thereon upon which the peripheral portion of said bimetallic disc freely rests, a motion transmitting means engaging said movable contact means and freely resting upon the center portion of said disc, and means providing 9 a threaded connection between said base and the said member whereby said base and interconnected member form a housing for enclosing the aforementioned switch elements and whereby the position of the disc and the operation of the switch are adjusted by relative rotation between the member and base. i

4. A thermostatic switch unit comprising a base, stationary electrical contact means mounted on said base, electrical contact means movable to and from engagement with said stationary contact means and normally biased to one of those positions, an imperforate convexoconcave bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature, a member having an annular portion with a surface thereon upon which the peripheral portion of said bimetallic disc freely rests, a motion transmitting means between said movable contact means and the central portion of said disc and having a free bearing engagement therewith, and means providing a threaded connection between said base and the said member whereby the latter mentioned interconnected elements form a housing for the aforementioned switch elements whereby the position of the disc and the operation of the switch are adjusted by relative rotation between the member and base.

5. A thermostatic switch comprising a base, a rst electrical contact mounted on said base, a resilient arm provided with a second electrical contact adjacent one end thereof, means supporting the other end of said arm upon said base in a position such that the second contact is movable to and from engagement with the rst contact and is normally urged to one of those positions, a dished bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having an imperforate central portion, an annular member interconnected with said base and forming a switch housing therewith; said member having an annular portion upon which the peripheral portion of said bimetallic disc is supported, motion transmitting means between said central portion of said disc and the said resilient arm and having a free bearing engagement with said central portion of said disc, and means providing a threaded connection between said base and the said member whereby the position of said disc relative to said base and the operation of said switch are adjusted by relative rotation between the member and base.

6. A thermostatic switch as dened in claim wherein the said arm is suiciently flexible to bow towards said base intermediate its ends when said rst contact is held in engagement with said second contact by said bimetallic disc whereby a wiping action is elfected between said contacts when said bimetallic disc reverses its direction of curvature upon attainment of a predetermined temperature.

7. A thermostatic switch unit comprising a base, a first electrical contact mounted on said base, a resilient arm provided with a second electrical contact adjacent one end thereof and an opening intermediate its ends, means supporting the other end of said arm upon said base in a position such that the second contact is movable to and from engagement with the rst contact and is normally urged to one of said positins by the resiliency of said arm, an imperforate conVeXo-concave bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature, an annular member interconnected with said base and forming a switch housing therewith, said annular member having a surface upon which the peripheral portion of said bimetallic disc is supported, motion transmitting means having a portion received in the opening of said arm and another portion abutting the center of said disc with a free bearing engagement, and means providing a threaded connection between said base and the said member whereby the position of said disc relative to said base and the 10 operation of said switch are adjusted by relative rota# tion between the member and base.

8. A thermostatic switch comprising a base, means mounted on said base providing an electrical contact surface, a resilient arm provided with an electrical contact adjacent one end thereof, means supporting the other end of said arm upon said base in a position such that the contact on said arm is normally biased from engagement with the said contact surface but is movable into engagement with said contact surface, a conveXo-concave bimetallic disc adapted to reverse its curvature upon attaining a predetermined temperature and having an imperforate center portion, an annular member interconnected with said base and forming a switch housing therewith, said annular member having a surface upon which said bimetallic disc is supported adjacent its periphery, a motion transmitting member between said disc and arm engaging the disc substantially at the center portion thereof with a free bearing engagement and engaging the arm intermediate its ends, the etfective length of the last-mentioned member being greater than the least distance between the undeected arm and the central portion of the disc when the latter is curved to effect contact engagement, whereby the said movable contact engages the said contact surface before the bimetallic disc has completed ilexure to its position causing contact engagement so that when the disc has fully reached that position the said a-rm is ilexed intermediate its ends towards said base thereby producing a wiping action between said movable contact and contact surface, and means providing a threaded connection between said base and the first-mentioned member whereby the position of the disc relative to said base and the operation of said switch are adjusted by relative rotation between the first-mentioned member and base.

9. A thermostatic switch as defined in claim 8 and further comprising means on said base limiting the liexure of said arm.

l0. A thermostatic switch comprising a base, a stationary electrical contact mounted on said base, a resilient arm provided with an electrical contact adjacent one end thereof and an opening intermediate its ends, means supporting the other end of said arm upon said base in a manner such that the contact on said arm is normally biased from engagement with the stationary contact and is movable into engagement therewith, a convexe-concave bimetallic disc adapted to reverse its curvature upon attaining a predetermined temperature and having an imperforate central portion, an annular member interconnected with said base and forming a switch housing therewith, said annular member having a planar surface upon which the peripheral portion of said bimetallic disc is supported, a motion transmitting pin having one end in free bearing engagement with the central portion of said disc and a reduced diameter portion at the other end extending through the opening in said arm, an abutment surface on said base aligned with the said other end of said pin for engagement thereby, the dimensions of said pin and abutment being such that the former contacts the latter in response to action of said disc only after the contacts have engaged thereby producing a wiping action between the latter, and means providing a threaded connection between said base and member whereby the position of the disc relative to the base and the operation of the switch may be adjusted by relative rotation between the base and member.

l1. A thermostatic switch comprising a base, stationary electrical contact means mounted on said base, movable electrical contact means movable to and from engagement with the stationary contact means and normally biased to one of those positions, a convexe-concave bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having an imperforate central portion, a member interconnected with said base and forming a switch housing therewith, said member having a surface upon which the said bimetallic disc is freely supported adjacent its periphery, a force transmitting member extending between the central portion of said bimetallic disc and the movable contact means and having a free bearing engagement with said cent-ral portion, a cylindrical ilange extending outwardly from said base member with the said contact means and bimetallic disc disposed therein, and cooperating screw threads upon said ange and the disc supporting member whereby the position of the disc relative to the base and the ope-ration of the switch may be varied by rotating the last-mentioned member relative to the flange.

12. A thermostatic switch comprising a switch housing including a base provided with an outwardly extending cylindrical flange having a screw thread on the wall thereof, a stationary electrical contact mounted on said base within said flange, a resilient arm provided with an electrical contact adjacent one end thereof, means supporting the other end of said arm upon said base within said flange in spaced relationship from the stationary contact in a manner such that the contact on said arm is movable to and from engagement with the stationary Contact, the movable contact being normally biased from engagement with the stationary contact by the resiliency of said arm, a member provided with a screw thread mating with the thread on said ange and having an annular planar surface disposed towards said base, a convexe-concave bimetallic disc with its periphery freely resting upon said surface and having an imperforate central portion, and motion trans mitting means between said disc and arm and having a free bearing engagement with said central portion whereby the movable contact is moved to and from engagement with the stationary contact in response to reversal of curvature of the bimetallic member upon predetermined changes of temperature with the operation of said switch being adjusted by rotating said member relative to said flange.A

13. A thermostatic switch comprising a base, a plurality of stationary electrical contacts mounted in spaced relationship upon said base, a rigid electrical conductive member movable to and from bridging engagement with said stationary contacts, spring means between said base and conductive member acting in a direction to urge said conductive member to a predetermined position relative to said stationary contacts, a convexe-concave bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having an imperforate center portion, a member interconnected with said base and forming a switch housing therewith, said member having an annular planar surface upon which the bimetallic disc is supported adjacent its periphery with the center portion of said disc free to move, a motion transmitting means between the center portion of said bimetallic disc and said conductive member and having a free bearing engagement with said center portion, and cooperating screw threads intermediate said base and disc supporting member whereby the operation of said switch may be regulated by relative rotation between the base and the disc supporting member.

14. A thermostatic switch comprising a base member, a plurality of stationary electrical contacts mounted upon said base member in spaced relationship to the latter and to each other, a rigid electrical conductive member adapted to be moved to and from bridging engagement with said stationary contacts, spring means between said base and conductive member normally acting to maintain the latter in engagement wit l the said contacts, a cylindrical flange extending outwardly from said base member with the said stationary contacts and conductive member disposed, therein, a convexe-concave bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperat'ure and having an imperforate central portion, a member interconnected with said base member and forming a switch housing therewith, said member having an annular planar surface upon which the bimetallic disc is supported adjacent its periphery Y i295 with the central portion of said disc free to move, a motion transmitting means between the central portion of said bimetallic disc and said conductive member and having a free bearing engagement with said central portion, and cooperating threads upon the interior of said iiangc and the exterior periphery of said disc supporting member whereby the operation of said switch may be regulated by -relative rotation between the base and disc supporting members.

15. A thermostatic switch comprising a base, a plurality of stationary electrical contacts mounted in spaced relationship upon said base, a rigid electrical conductive member movable to and from bridging engagement with stationa-ry contacts, spring means between said base and conductive member normally acting to separate the said member from the said contacts, a member interconnected wth said base and forming a switch housing therewith, said member having an annular' planar surface, a conveXo-concave bimet'allic disc resting upon said surface with the center portion of said disc being imperforate and free to move in response to change in temperature, a motion transmitting means between the center portion of said bimetallic disc and said conductive member and having a free bea-ring engagement with said center portion of said disc, and means adjustably interconnecting said base and disc supporting member including cooperating screw threads whereby the operation of said switch may be regulated by relative rotation between the base and disc supporting member.

16. A thermostatic switch comprising a substantially cup-shaped housing member having an annular surface on the interior thereof, a convexe-concave bimetallic disc freely resting upon said surface in the region of the periphery of the disc and having the central portion thereof unsupported, a base member, cooperating screw threads upon said cup-shaped member and upon said base member whereby said members are relatively adjustable, stationary electrical contact means mounted upon said base member, electrical contact means movable to and from engagement with the stationary contact means and normally biased to one of those positions, and motion transmitting means between the center of said disc and said movable contact means whereby said movable contact means is moved relative to the stationary contact means when the bimetallic disc reverses its curvature upon attaining a predetermined temperature and the operation of said switch is adjusted by etecting relative rotation between the base and cup-shaped members.

17. A thermostatic switch comprising a substantially cup-shaped housing member having an annular planar' surface on the interior thereof, a convexe-concave bimetallic disc freely resting upon said surface in the region of the periphery of the disc and with the central portion thereof unsupported, a base member, cooperating screw threads upon the interior of said cup-shaped member and upon the periphery of said base member whereby said members are relatively adjustable, stationary electrical contact means mounted upon said base member, electrical contact means movable to and from engagement with the stationary contact means, means normally biasing said movable contact means from engagement with the stationary contact means, and motion transmitting means between the center of said disc and said movable contact means, whereby said movable contact means s moved relative to the stationary contact means when the bime tallic disc reverses its curvature upon attaining a predetermined temperature and the operation of said switch is adjusted by eiecting relative rotation between the base and cup-shaped members.

i8. A thermostatic switch comprising a base member, a plurality of stationary electrical contacts mounted in spaced relationship uponV said base member, a rigid electrical conductive member movable to and fromengagement with said contacts, guide means'carried .by said base member cooperating with said conductive member to constrain its movement to a predetermined path, spring means between said base member and conductive member tending to move the latter away from the former, a cup-shaped housing member having an interior annular planar surface spaced beneath the rim thereof, a convexoconcave bimetallic disc supported in the region of its periphery upon said surface with the central portion of said disc unsupported, a motion transmitting means between the central portion of said disc and said conductive member, and cooperating screw threads upon said cupshaped member and said base member whereby the operation of said switch may be regulated by relative rotation between the base and cup-shaped members.

19. A thermostatic switch comprising a base member, a plurality of stationary contacts mounted in spaced relationship upon said base member, a guide member supported upon said base member and extending at right angles from the face thereof carrying said stationary contacts and substantially centrally of the latter, a rigid conductive disc adapted to engage and bridge said stationary contacts, the said disc having a central opening through which said guide member extends, spring means between said base and conductive disc normally acting to separate the said disc from the said contacts, a cup-shaped housing member having an interior annular planar surface spaced beneath the rim thereof, a convexo-concave bimetallic disc supported in the region of its periphery upon said surface with the center portion of said bimetallic disc unsupported, a motion transmitting means between the central portion of said bimetallic disc and said conductive disc, and cooperating screw threads upon said cup-shaped member and the said base member whereby the operation of said switch may be regulated by relative rotation between the base and cup-shaped members.

20. A thermostatic switch comprising a base member provided with a threaded portion, a supporting member for a bimetallic disc and having a threaded portion cooperating with the threaded portion of the base member whereby said members are adjustably interconnected, said supporting member having a supporting surface 1ocated in a plane parallel to the side of said base member which is adjacent to said supporting surface, stationary contact means carried by said base member and extending from said side thereof toward the plane of said supporting surface, a contact means movable to and from engagement with the stationary contact means and normally biased to one of those positions, a dished bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having its periphery freely supported by said supporting surface of said supporting member, and motion transmitting means between the center of said disc and said movable contact means wherefore relative rotation between said base member and said supporting member varies the distance between said side of said base member and said disc to adjust the operation of said switch.

21. A thermostatic switch comprising a base member having a substantially cylindrical extension projecting from one side of the base member adjacent the periphery of the latter, said extension at its free end being provided with internal screw threads, a ring-like member having an internal annular shoulder providing a supporting surface located in a plane parallel to the plane of the inner side of the base member within said cylindrical extension, said ring-like member being provided externally with threads wherefore said ring-like member can be adjustably screwed into the internally threaded free end of said extension to vary the distance between the supporting surface of the ring-like member and the inner side of the base member, stationary contact means mounted on said base member and extending within said cylindrical extension, contact means movable to and from engagement with the stationary contact means and normally biased to one of those positions, a dished bimetallic disc adapted to reverse its direction of curvature upon attaining a predetermined temperature and having its peripheral portion freely supported upon said supporting surface of said ring-like member, and motion transmitting means between the center of said disc and said movable contact means, wherefore screwing said ring-like member inwardly or outwardly of said cylindrical extension varies the distance between the inner side of the base member and said disc to adjust the operation of the switch.

References Cited in the le of this patent UNITED STATES PATENTS 1,725,296 Paige Aug. 20, 1929 1,733,085 Thomas Oct. 22, 1929 1,897,316 Marshall Feb. 14, 1933 1,972,832 Spencer Sept. 4, 1934 2,015,545 Bletz et al. Sept. 24, 1935 2,060,836 Taxner Nov. 17, 1936 2,230,770 Van Almelo Feb. 4, 1941 2,238,881 Evans Apr. 22, 1941 2,508,991 Butler May 23, 1950 

